A bank robber was shot to death Friday by an off-duty Houston police officer who had gone to the business with a colleague to make a deposit, officials said.

Two other men were arrested after the robbery at Regions Bank, 7044 E. FM 1960 in Humble.

Three armed men entered the bank about 2 p.m. and demanded money, said Harris County Sheriff's Office spokesman Deputy Thomas Gilliland. One of the men had a shotgun, and two were toting pistols.

The robbers fled the bank with an undisclosed amount of cash and were getting into a Ford Explorer when they were confronted in the parking lot by one of two off-duty officers with HPD's Marine Unit. The officers were in uniform, a blue shirt identifying them with the unit.

By chance, Gilliland said, one of the HPD officers had arrived to do business at the same bank. His colleague waited in a personal vehicle.

"As they were entering their vehicle, one of the officers ordered them to drop their weapons," Gilliland said. "The passenger in the vehicle pointed a shotgun at the officer, and he (officer) fired once, killing him."

After the gunfire, the vehicle accelerated about 50 feet onto the sidewalk where it came to a stop before rolling into a dentist's office. The car struck the front door of the business.

Two sheriff's deputies responding to the alarm arrested the other two men a short distance from the Explorer. No other injuries were reported.

Two hours after the incident, the dead man's body remained slumped out of the driver's side of the Explorer, where he tried to crawl out after he was shot, Gilliland said.

An EMS unit checked out several bank employees who were shaken up by the robbery.

"There was some frayed nerves and an amount of anxiety among the employees, which is certainly understandable," Gilliland said.

The case was under investigation by the FBI Bank Robbery Task Force and the Harris County Sheriff's Office.